I have a couple of MacBooks. Using a Trifield EMF meter with radio/microwave capability, if I hold the meter near the laptop (where I understand the wifi antenna is located), I receive blips ranging from 4-10 milligauss. In Radio/Microwave mode it does blips from 0.1 to about 1.5 mW/cm^2).

The router itself, near its antenna, does movement between about 0.5 to 2.5 (0.5mW/cm^2 to 2.5/cm^2). No wireless devices are connected, but the wireless antenna is turned "on" (cannot be turned off).

I work in a high security field and am wondering if the wifi is actually transmitting even though it is set to "off" in the operating system. E.g., due to a root kit or other virus.

Can other components in a MacBook cause quick fluctuations of this much? I would expect it to remain mostly constant if Bluetooth/wifi were not transmitting

  • I am not sure that using an RF meter is the proper way to deal with a suspect virus in your network... – Vladimir Cravero Jan 28 '16 at 21:37
  • @VladimirCravero WiFi sniffer would be a better tool. But if a meter is what's available, then why not give it a try. – Nick Alexeev Jan 28 '16 at 23:05

The answer is yes all electronics emit EMF but especially digital electronics because there are millions of gates switching on and off and the PCB traces function as antennas so there will be lots of EMF. There's an FCC limit that every device has to pass but I won't get into that. Your EMF meter is going to measure most of the EMF from the laptop. What you want to do is zoom in on the frequencies in the 2.4GHz band (for bluetooth and wifi). You need a spectrum analyzer, and you need to know how to use it. SDR Hackaday


Wifi and bluetooth traffic is easy enough to check for. Any number of 802.11x or Bluetooth devices support a promiscuous monitor mode. It allows a passive checking of all standard formatted traffic.

To check if the wifi or bluetooth module is mostly off, you could wire in a ammeter. I believe the last five years, these modules are now non optional, but still modular, so you'd have to take the laptop apart to reach them. Alternatively you could just disconnect them.

The small amount of EMF you are seeing would be from the high frequency switching done by the cpu, gpu, and even the battery regulator. You could do a baseline by checking multiple laptops.

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